Method of manufacturing files for stencilizing stencil sheets



I Jam 3, V 1933.

S. HORil METHOD OF MANUFACTURING FILES FOR STENCILIZING STENCIL SHEETS Filed July 21, 1930 0000 90060 0 $0 0 '0 o o o:

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Patented Jan. 3, 1933 UNETED STATES PATENT OFFIQE SHINJIRO HOBII, F TOKYO, JAPAN Application filed July 21, 1930, Serial No. 469,616, and in Japan August 7, 1929.

My invention relates to an improved file for use in stencilizing the stencil sheet for duplicator by a cooperation with a hand stylus.

Heretofore, the file employed for such purpose has been manufactured according to a method substantialy similar to that of manufacturing ordinary double-cut dead-smooth file for abrading, reducing and smoothing metal or other resistant materials. I11 the existing method, each series or ridges is cut by a chisel placed on the blank with an inclination from the perpendicular of 12 or 14, so that the ridges or teeth are accordingly inclined from the perpendicular. Therefore, when the stencil sheet is stencilized by a hand stylus, placing the sheet on such file having inclined teeth, the stencil sheet is unduly cut when the tip of the hand stylus is drawn in the direction reverse to the direction of inclination of the teeth, whereas when the tip of the hand stylus is drawn in the direction of the inclination of the teeth it results in insufiicient strength of stencilizing effect.

Consequently, it is not possible by the existing r file to obtain uniform stencilizing cut in all directions.

I have already proposed to make a special file particularly suited for stencilizing purpose by cutting perpendicular teeth, employing an ordinary V-shaped chisel but placing it on the blank perpendicularly. On microscopic investigation, however, I have found that even the chisel is placed on the blank perpendicularly the center lines of the V- shaped grooves formed thereby are not perpendicular, but are considerably inclined.

It is one object of my invention to manufacture a novel file suited for stencilizing the stencil sheet for a duplicator, in which true perpendicular grooves and consequently true perpendicular teeth are formed and, as a consequence, the latter have uniform stenciling effects in all directions.

In the accompanying drawing Figure 1 is a plan view of the file made according to my invention.

Figure 2 is an enlarged sectional view illustrating my old method intended for cutting the perpendicular grooves on the blank of the file.

Figure 3 is a similar view illustrating my improved method of cutting true perpendicular symmetrical V-shaped grooves on the blank.

In Figure 2, which illustrates my old method of cutting V-shaped grooves, 1 is the blank of the file, and 2 is a V-shaped chisel with its front and back sides inclined equally from the perpendicular. 3 are the V-shaped grooves cut by said chisel 2. From the drawing it will be seen that these grooves 3 have been considerably deformed, and that the original center line 4a has been shifted from the perpendicular to an inclined position 45. This is due to the fact that when cutting the next groove the material forming the ridge 6 at the front side of the chisel 2 has been displaced into the groove lying just in front of same because of the difierence of strength of materials of the blank in the front and back of the chisel. Chain lines 5 show the original forms of the symmetrical V-shaped grooves. Hence, in the file made according to my old method, in spite of using a perpendicularly placed chisel, center lines of all grooves and teeth are considerably inclined toward the end of the file at which the cutting operation started, with the exception that only one groove which has been cut lastly is perpendicular and symmetrical.

Now, according to my improved method, I first cut a V-shaped groove which is not symmetrical having its back side (right hand side in the drawing) inclined greater than its front side (left hand side) as shown in Fig. 3 in chain lines 5'. In other words, a V-shaped groove is cut which has the center line slightly inclined toward the blank portion. For that purpose, it is preferred to use a chisel 2 having one side inclined greater tllian the other with respect to the perpendicu ar.

When the next groove is cut, the material forming the ridge 6' in front of the chisel will be slightly displaced into the first groove, so that the latter will be deformed into a desired symmetrical V-shaped groove 3 having its center line positioned perpendicularly, as shown in Figure 3.

From the foregoing, it will be seen that in the file made according to my invention, all grooves and consequently all teeth are truly perpendicular, so that when in use the tip of the hand stylus can be run smoothly in all directions, and stencil sheet can be uniformly stencilized.

An ordinarydouble-cut fileused-tor abrading or-smoothing resistant materialshas two series of straight cuts crossing each other at an acute or obstuse angle. In contradistinction'to such arrangement, I have found on- 7 experiencesthatnfor the file to be used for stencilizing certain letters or designs it'is advisable that two sets of straight cuts across each other at right angle or nearly so, as shown inv Fig. -1. With the length of the file, both sets of straight ridges may be cut.

at an; angle of45 as shown, or at some other angle. a

. What I claim is A method of manufacturing a file for stencilizing stencil sheets, comprising cutting a V -shaped groove having its center line slight- 1y inclined, from, the perpendicular toward the direction of the blank portion, with. a chisel having its back side inclined at a great er angle than that ofitscfront side by placing said chisel perpendicularly on the blank with its backside facing toward the blank portion,

and then,,upon cutting next similar groove, automatically displacing the material of the ridge net in front of the chisel by the chisel into the first groove, so that the latter is deformed into asymmetrical V -shaped groovewith its center line positioned perpendicularly. H

I-ntestimony whereof I afiix my signature.

SHINJIRO HORII. 

